Method and apparatus for forming a thin film

ABSTRACT

In a method of uniformly forming a thin film on a wafer and an apparatus of using the same, after supplying a first gas, a second gas and a third gas into a reaction chamber in which a wafer is loaded, a thin film is formed on the wafer from the first gas and the second gas. The third gas stabilizes the second gas. A wafer holder is disposed in the reaction chamber. A gas-supplying unit extended to the reaction chamber supplies more gas to the central portion of the wafer than to a peripheral portion of the wafer. The contaminant particles formed from the second gas are removed by using the gas-supplying unit and the third gas. The first gas is supplied more at the central portion of the wafer than at a peripheral portion of the wafer, thereby forming a thin film of high quality on the wafer.

RELATED APPLICATIONS

[0001] The present application claims priority from Korean PatentApplication No. 2003-09927, filed on Feb. 17, 2003, the contents ofwhich are hereby incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a method and an apparatus forforming a thin film uniformly on a wafer with improved characteristics,and more particularly, to a method of producing plasma from a first gasand a second gas to form a layer on a wafer while contaminant particlesproduced from the second gas are removed to form a thin film uniformlyon the wafer with improved characteristics and an apparatus forperforming the same.

[0004] 2. Description of the Related Art

[0005] Recent advances in semiconductor devices tend to be in highintegration and high performance for processing more data in a shortertime. To manufacture highly integrated high-performance semiconductordevices, a technique of depositing a thin film precisely on asemiconductor substrate is important.

[0006] Generally, techniques of depositing a thin film on a wafer can bedivided into physical vapor deposition (PVD) using a physical method andchemical vapor deposition (CVD) using a chemical method.

[0007] In physical vapor deposition, a heater is installed and a sourcematerial is placed on the heater. A source material is disposed in anupper portion of a chamber under a high vacuum condition. The waferseparated from the heater is disposed in the chamber. When the heaterheats a source material to a high temperature, the source materialevaporates and is consolidated on the wafer to form a thin film.

[0008] In physical vapor deposition, metal particles are separated froma target to form a metal thin film using an argon gas ionized by a highvoltage. However, physical vapor deposition is used in limited processesbecause it typically results in formation of a non-uniform film.

[0009] In chemical vapor deposition, a semiconductor layer or aninsulating layer of a single crystal is formed on a surface of the waferusing a chemical reaction of a source material. The chemical vapordeposition may be a low-pressure chemical vapor deposition (LPCVD), anatmospheric pressure chemical vapor deposition (APCVD), a plasmaenhanced chemical vapor deposition (PECVD) and a high-pressure chemicalvapor deposition (HPCVD), according to a pressure in a chamber. Chemicalvapor deposition is used to deposit thin films such as an amorphoussilicon layer, a silicon oxide layer, a silicon nitride layer or asilicon oxynitride layer on the wafer.

[0010] In plasma enhanced chemical vapor deposition, electrons of highenergy collide with the neutral gas molecules to decompose the gasmolecules, and the thin film is deposited by using deposition ofdecomposed gas atoms on a semiconductor substrate. Plasma is formed froma precursor gas in a chamber while depositing the thin film at arelatively high deposition rate at a low temperature. However, inchemical vapor deposition, when step coverage of the thin film is notgood, voids may be formed in the thin film. As the depositing processprogresses and the gap between patterns decreases, the voids increase.The voids formed in the thin film cause many problems such asdeteriorating characteristics of the thin film and increased failures ofsubsequent processes.

[0011] In order to solve the problems of the plasma enhanced chemicalvapor deposition method, a chemical vapor deposition using ahigh-density plasma chemical vapor deposition (HDP-CVD) has been used.In the high density plasma chemical vapor deposition, as an etchingprocess using sputtering is performed while depositing the thin film,the thin film is formed without voids in a gap of high aspect ratio.However, when a gap width is shortened or multiple thin film depositionsare performed, the HDP-CVD also may not fill up the gap without thevoids because silicon oxide etched during the sputtering process isre-deposited. When silicon oxide is re-deposited, an overhang structurein the silicon oxide layer is formed. The overhang structure may formthe voids in the thin film. The overhang structure is disposed on acorner of the pattern. Recently, a number of process steps such asadding an etching gas to a source gas and controlling temperature of thewafer are performed to solve the problems of HDP-CVD.

[0012]FIG. 1A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 700 W was applied to form an oxide layer on a central portion of awafer, and FIG. 1B is a Scanning Electron Microscope (SEM) imageillustrating a cross-sectional view of an oxide layer according to aconventional method of an HDP-CVD of adding an etching gas, when a biaspower of about 700 W was applied to form an oxide layer on a peripheralportion of a wafer.

[0013] Referring to FIGS. 1A to 1B, when a bias power of about 700 W issupplied, voids and porous layers 13, 14 are formed on each of the thinfilm patterns of a central portion and a peripheral portion of a waferto deteriorate gap fill characteristics of a thin film. An upper portion15, 16 of the deposited thin films on the central portion and theperipheral portion of the wafer are non-uniform, and the thin filmdeposited on the central portion is more uniform than the thin filmdeposited on the peripheral portion. The films having the non-uniformitycause numerous defects.

[0014]FIG. 2A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 900 W was applied to form an oxide layer on a central portion of awafer, and FIG. 2B is a Scanning Electron Microscope (SEM) imageillustrating a cross-sectional view of an oxide layer according to aconventional method of an HDP-CVD of adding an etching gas, when a biaspower of about 900 W was applied to form an oxide layer on a peripheralportion of a wafer.

[0015] Referring to FIGS. 2A to 2B, when a bias power of about 900 W issupplied, voids and porous layers are not formed on a central portion ofa wafer, thereby having good gap fill characteristics. An upper portion25 of the thin film is uniform. However, voids and porous layers areformed on a peripheral portion 22 of a wafer. The gap fillcharacteristics of FIG. 2B are better than the gap fill characteristicsof FIG. 1B. But, the thin film of FIG. 2B may also cause defects.

[0016]FIG. 3A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 1,100 W was applied to form an oxide layer on a central portion ofa wafer, and FIG. 3B is a Scanning Electron Microscope (SEM) pictureillustrating a cross-sectional view of an oxide layer according to aconventional method of an HDP-CVD of adding an etching gas, when a biaspower of about 1,100 W was applied to form an oxide layer on aperipheral portion of a wafer.

[0017] As shown in FIGS. 1A to 3B, in accordance with a conventionalmethod of an HDP-CVD of adding an etching gas, the gap fillingcharacteristics are greatly varied according to an increase in the biaspower.

[0018] Referring to FIGS. 1A and 1B, when a bias power of about 700 W isapplied, voids are formed in each thin film formed in a central portion11 and a peripheral portion 12 of the wafer. Further, porous thin filmsare formed in the central portion 11 and the peripheral portion 12.Thus, unpreferable gap-filling characteristics are shown. The upperportions 15, 16 of the thin film formed in the central portion 11 and aperipheral portion 12 of the wafer shows non-uniformity that increasesfrom the central portion 11 towards the peripheral portion 12. The thinfilms as shown in FIGS. 1A and 1B are inadequate for use and thusdiscarded.

[0019] When a bias power of about 900 W is applied, no void is formed ineach film formed in the central portion 21 as shown in FIG. 2A. Also, noporous film is formed in the central portion and the upper portion. 25of thus formed thin film shows uniformity. Thus, good gap-fillingcharacteristics are shown. However, as shown in FIG. 2B, voids areformed in the thin film formed in the peripheral portion 22 of thewafer. Also, a porous film is formed in the peripheral portion 22.Further, the uniformity of the upper portion 26 of the deposited thinfilm is better than the thin layer as shown in FIG. 1B. However, theupper portion 26 is somewhat non-uniform in thickness and thus mayinduce a failure in a subsequent process.

[0020] Referring to FIGS. 3A to 3B, when a bias power of about 1,100 Wis applied, voids and porous layers are not formed in each of the thinfilm patterns of a central portion 31 and a peripheral portion 32 of awafer to have good gap filling characteristics. Upper portions 35, 36 ofthe thin films formed on the central portion 31 and the peripheralportion 32 of the wafer are uniform. However, an upper portion 33 of apredetermined layer disposed under the thin film is over-etched, therebygenerating a clipping phenomenon.

[0021] Generally, when the deposition process is performed on thepatterns having a short gap width and a number of thin films isincreased, silicon oxide etched by sputtering is re-deposited on aperipheral region of the patterns. Since the re-deposition causesgeneration of the voids in the thin film, a proper bias power suitablefor filling the gap is applied to the patterned region having the gap.However, when a bias power is increased to more than a predeterminedpower, a corner of a silicon oxide layer is over-etched in a directionof about 45 degrees to cause the clipping phenomenon. Therefore,improvement in layer characteristics by increasing the bias power islimited.

[0022] An apparatus for performing a chemical vapor deposition processcomprises a reaction chamber in which gases are chemically reacted witheach other. A dielectric layer, a conductive layer or an insulatinglayer is deposited on a substrate using a gas reaction in the reactionchamber. During the deposition process of the thin film, not only is thethin film formed on a substrate, but the thin film is also formed onvarious structures such as a masking structure in the reaction chamberor a substrate-supporting structure, thereby forming contaminantparticles in the reaction chamber. During a subsequent depositionprocess of the thin film, a crack is formed in the layer and the layeris peeled off so that the contaminant particles may drop on thesubstrate. The layer is formed on the inner wall of the reaction chamberor the various structures. In order to improve deposition efficiency,the reaction chamber is cleaned regularly to remove the contaminantparticles. The cleaning is performed by means of introducing an etchinggas having fluorine such as trifluoro-nitrogen (NF₃). The fluorineetches silicon, silicon oxide, etc., using an ion impact of a plasmareaction to remove the contaminants deposited on the inner wall of thereaction chamber. However, after the cleaning, fluorine contaminantsremain in the reaction chamber to degrade the quality of the thin filmthat is subsequently deposited. For example, voids may be formed in anamorphous silicon thin film formed on a silicon nitride layer. In orderto reduce damage caused by the fluorine contaminants, a length of anozzle that supplies,the etching gas is controlled and an amount of apower supply is increased. However, the control of the length and theincrement of the power supply cause a formation of non-uniform thin filmon the wafer.

[0023]FIG. 4 is a sectional view illustrating an HDP-CVD apparatus, andFIG. 5 is a partial perspective view illustrating an enlargedgas-supplying unit of the HDP-CVD apparatus in FIG. 4.

[0024] Referring to FIGS. 4 and 5, the conventional HDP-CVD comprises areaction chamber 10, a wafer holder 30 for supporting a wafer 40, anelectrostatic chuck 20 installed on the wafer holder 30, a reactiongas-supplying tube 50 and a purge gas-supplying tube 60.

[0025] An upper portion of the reaction chamber 10 has a dome shape, anda radio frequency (RF) coil 80 is disposed on an outer portion of thereaction chamber 10. The wafer holder 30 is disposed on an inside of thereaction chamber 10, and the electrostatic chuck 20 is installed on thewafer holder 30. The reaction gas-supplying tube 50 is disposed on theinside of the reaction chamber 10. The reaction gas-supplying tube 50 isdisposed on the reaction chamber 10 relative to a central axis of theelectrostatic chuck 40 in regular intervals. Generally, a reactiongas-supplying tube 50 supplies a source gas for depositing a thin filmand an etching gas for improving deposition efficiency. A purgegas-supplying tube 60 is disposed below the reaction gas-supplying tube50. The reaction gas-supplying tube 50 is a tube having a predetermineddiameter, and a nozzle is inclined toward a center of the upper portionof the reaction chamber 10. A vacuum pump 70 is disposed on a side ofthe reaction chamber 10.

[0026] When the wafer 40 is mounted on the electrostatic chuck 20, thevacuum pump 70 controls a pressure in the reaction chamber 10. Areaction gas for depositing the thin film is supplied through thereaction gas-supplying tube 50. In order to improve the depositionefficiency, the etching gas is supplied together with the reaction gas.After the reaction gas and the etching gas are supplied into thereaction chamber 10, a bias power from an RF power-supplying unit issupplied to the wafer holder 30. When the bias power is supplied, plasmais formed in the reaction chamber 10 and the thin film is deposited onthe wafer 40.

[0027] An interval between patterns of a thin film formed on asemiconductor substrate decreases according to a high integration and ahigh performance of a semiconductor device. As the interval between thepatterns decreases, the deposition efficiency is deteriorated.Therefore, an etching gas is needed. Generally, a gas having fluorine isused as the etching gas. However, the fluorine residues remain in thereaction chamber to deteriorate characteristics of the thin film formedon the wafer. Also, contaminants formed by means of an etching gas aredeposited on an inside wall of the reaction chamber and structures (orparts) in the reaction chamber such as a cover or a substrate supportingstructure to form contaminant particles. During the subsequentdeposition process of the thin film, a crack is formed in thecontaminant particles deposited on the inner wall of the reactionchamber or the contaminant particles are removed from the inner wall.Therefore, the contaminant particles may drop on the substrate, and thesemiconductor device may become damaged or defective.

[0028] In order to reduce the damage or the defects, a length of theetching gas-supplying tube is preferably shortened and the bias power ispreferably increased. However, when the length of the etchinggas-supplying tube is shortened, the thin film on the wafer is formednon-uniformly. Also, when the bias power increases, energy ofhigh-density plasma is also increased to non-uniformly etch the thinfilm on the wafer. Over-etching causes re-deposition and clipping. Also,an over-etched portion and under-etched portion are formed on the wafer,thereby causing problems in subsequent processes.

SUMMARY OF THE INVENTION

[0029] In an exemplary embodiment of the present invention, the presentinvention provides a method of forming a thin film by convertingcontaminant particles generated from gases into another stablecomposition to deposit a thin film of high quality uniformly on a waferwith improved characteristics.

[0030] In another exemplary embodiment of the present invention, thepresent invention provides an apparatus for depositing a thin film bysupplying gases to deposit the thin film to have a uniform thickness.

[0031] In another exemplary embodiment of the present invention, thepresent invention provides an apparatus for depositing a thin film bysupplying gases for depositing the thin film, and converting contaminantparticles generated from the gases for improving characteristics of athin film to another stable composition to deposit a thin film of highquality on a wafer uniformly, in which a flow rate of the gas fordepositing the thin film at a central portion of a semiconductorsubstrate is greater than at a peripheral portion of the semiconductorsubstrate.

[0032] According to a method of the invention, first gas for forming athin film on a semiconductor substrate, a second gas for improvingcharacteristics of the thin film, and a third gas for stabilizing thesecond gas are supplied onto a semiconductor substrate. The thin film isthen formed on the semiconductor substrate using a plasma gas of thefirst gas and a plasma gas of the second gas.

[0033] The first gas may be at least one gas such as asilicon-containing gas, an oxygen-containing gas, a nitrogen-containinggas and an inert gas. The second gas may include a fluorine-containinggas, and the third gas may include a hydrogen-containing gas. An oxidelayer or a nitride layer may be uniformly formed on the semiconductorsubstrate.

[0034] The first gas may include at least one of a silane gas, an oxygengas, a nitrous oxygen gas, a nitrogen gas, a helium gas and an argongas. The second gas may include a trifluoro-nitrogen gas. The third gasmay include a hydrogen gas.

[0035] The forming of the thin film may include forming an oxide layeror a nitride layer on the semiconductor substrate.

[0036] In one embodiment, the flow rate of the first gas at a centralportion of the semiconductor substrate is greater than that at aperipheral portion of the semiconductor substrate.

[0037] The apparatus for depositing a thin film comprises a reactionchamber, a wafer holder for supporting a wafer, and a gas-supplying unitextended into the reaction chamber to supply a gas. The flow rate of thesupplied gas at the central portion of the wafer is higher than that ata peripheral portion of the wafer. The wafer holder is disposed in thereaction chamber.

[0038] The gas-supplying unit includes at least one injector. Theinjector extends into the interior of the reaction chamber. In anotherexemplary embodiment of the present invention, a plurality of firstinjectors adjacent to the peripheral portions of the wafer and extendinginto the interior of the reaction chamber, and a plurality of secondinjectors adjacent to the central portion of the wafer and extendinginto the interior of the reaction chamber are formed, and an intervalbetween the first injectors and the peripheral portion of the wafer isshorter than an interval between the second injectors and the centralportion of the wafer. At least one of the first injectors and at leastone of the second injectors form at least one injector unit, and aplurality of injector units can be disposed in the interior of thechamber.

[0039] Another apparatus in accordance with the invention for depositinga thin film comprises a reaction chamber, a wafer holder disposed in thereaction chamber for supporting a wafer, and gas-supplying unit disposedin the reaction chamber for supplying the reaction chamber with a first,a second and a third gas. The first gas forms a thin film on the wafer,the second gas improves characteristics of the thin film, and the thirdgas stabilizes the second gas.

[0040] In one embodiment, the gas-supplying unit includes a plurality offirst injectors for supplying at least one of the first gas, the secondgas and the third gas, and a plurality of second injectors for supplyingat least one of the first gas, the second gas and the third gas.

[0041] An injector unit comprises at least one of the first injectorsand at least one of the second injectors. A plurality of the injectorunits is installed along an inner face of the reaction chamber. Aninterval between the first injectors and the peripheral portion of thewafer is shorter than an interval between the second injectors and thecentral portion of the wafer.

[0042] In one embodiment, the first gas includes at least one of asilicon-containing gas, an oxygen-containing gas, a nitrogen-containinggas and an inert gas. The second gas can include a fluorine-containinggas, and the third gas can include a hydrogen-containing gas. The firstgas can include at least one of a silane gas, an oxygen gas, a nitrousoxygen gas, a nitrogen gas, a helium gas and an argon gas. The secondgas can include a trifluoro-nitrogen gas. The third gas can include ahydrogen gas.

[0043] According to the present invention, contaminant particles fromthe gas for improving characteristics of the thin film are converted toanother stable composition, thereby improving the characteristics of thethin film formed on a semiconductor substrate and depositing the thinfilm with a uniform thickness by supplying a gas at a flow rate of thegas at a central portion of a semiconductor substrate being greater thanthat at a peripheral portion of the semiconductor substrate. Also, thecharacteristics of the thin film formed on a semiconductor substrate areimproved to reduce a defective proportion of subsequent processes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The foregoing and other objects, features and advantages of theinvention will be apparent from the more particular description of apreferred embodiment of the invention, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

[0045]FIG. 1A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 700 W is applied to form an oxide layer on a central portion of awafer.

[0046]FIG. 1B is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 700 W is applied to form an oxide layer on a peripheral portion ofa wafer.

[0047]FIG. 2A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 900 W is applied to form an oxide layer on a central portion of awafer.

[0048]FIG. 2B is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 900 W is applied to form an oxide layer on a peripheral portion ofa wafer.

[0049]FIG. 3A is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 1,100 W is applied to form an oxide layer on a central portion ofa wafer.

[0050]FIG. 3B is a Scanning Electron Microscope (SEM) image illustratinga cross-sectional view of an oxide layer according to a conventionalmethod of an HDP-CVD of adding an etching gas, when a bias power ofabout 1,100 W is applied to form an oxide layer on a peripheral portionof a wafer.

[0051]FIG. 4 is a sectional view illustrating an HDP-CVD.

[0052]FIG. 5 is a partial perspective enlarged view illustrating angas-supplying unit of the HDP-CVD of FIG. 4.

[0053]FIG. 6 is a sectional view illustrating an apparatus fordepositing a thin film according to the exemplary method of the presentinvention.

[0054]FIG. 7 is a partial perspective enlarged view illustrating angas-supplying unit of the apparatus of FIG. 6.

[0055]FIG. 8 is a graph illustrating uniformity of the thin film formedon the wafer using the apparatus of FIG. 6.

[0056]FIG. 9 is a graph illustrating uniformity of the thin film formedon the wafer according to another exemplary embodiment of the presentinvention.

[0057]FIG. 10 is a flowchart illustrating a method of forming a thinfilm according to another exemplary embodiment of the present invention.

[0058]FIG. 11 is a graph illustrating characteristics of the thin filmformed on the wafer according to another exemplary embodiment of thepresent invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0059]FIG. 6 is a sectional view illustrating an apparatus fordepositing a thin film according to the exemplary method of the presentinvention, and FIG. 7 is a partial enlarged perspective viewillustrating a gas-supplying unit of the apparatus of FIG. 6.

[0060] Referring to FIGS. 6 and 7, the apparatus for forming a thin filmof the exemplary embodiment of the present invention comprises areaction chamber 110, a wafer holder 130 disposed in the reactionchamber 110 for supporting a wafer 140, and gas-supplying unit 150extended into the reaction chamber 110 to supply a gas. The suppliedamount of the gas to the central portion of the wafer 140 is greaterthan that to a peripheral portion of the wafer 140.

[0061] An upper portion of the reaction chamber 110 includes a domeshaped housing 180, and a radio frequency (RF) coil 182 is disposed onan outer portion of the housing 180. The radio frequency coil 182provides the reaction chamber 110 with a radio frequency power.

[0062] The wafer holder 130 is disposed at a center in the reactionchamber 110, and an electrostatic chuck 120 is installed on the waferholder 130. A wafer 140 is disposed on the electrostatic chuck 120. Abias power having substantially the same frequency as that supplied fromthe radio frequency coil 182 is supplied to the wafer holder 140. In oneparticular exemplary embodiment, the frequency of the bias power isabout 13.56 MHz.

[0063] In order to control a predetermined pressure in the reactionchamber, a vacuum pump 170 is disposed on a side of the reaction chamber110, and a purge gas tube 160 is disposed adjacent to the vacuum pump170 to supply the reaction chamber 110 with a purge gas. The vacuum pump170 is selectively utilized according to a process performed in thereaction chamber 110.

[0064] The gas-supplying unit 150 comprises a first injector 152extended from the inner wall of the reaction chamber 110 towards aposition adjacent to the peripheral portion of the wafer 140 and asecond injector 154 extended from the inner wall of the reaction chamber110 towards a position adjacent to the central portion of the wafer 140.

[0065] The first injectors 152 and the second injectors 154 have atubular shape. The second injectors 154 are longer than the firstinjectors 152. Therefore, an interval between the first injectors 152and the peripheral portion of the wafer is shorter than an intervalbetween the second injectors 154 and the central portion of the wafer.Accordingly, the amount of the gas supplied by the second injectors 154to the central portion of the wafer 140 is more than the amount of thegas supplied by the first injectors 152. The first injectors 152 aredisposed in parallel with the second injectors 154. At least one of thefirst injectors 152 and at least one of the second injectors 154 form atleast one injector unit. A plurality of injector units is disposed alongthe inside of the reaction chamber at uniform intervals. Thegas-supplying unit 150 has a plurality of the injector units. The firstinjectors 152 and the second injectors 154 supply different gasesaccording to a kind of the thin film deposited on the wafer 140 into thereaction chamber 110, or the first injectors 152 and the secondinjectors 154 may supply substantially the same gas.

[0066] In an exemplary embodiment of the present invention, the gassupplied into the reaction chamber 110 comprises a source gas forforming the thin film on the wafer 140, a process gas for improving thecharacteristics of the thin film and a stabilizing gas for removingcontaminant particles from the process gas. The source gas is selectedaccording to a kind of the thin film formed on the wafer 140. Forexample, in order to form a silicon oxide layer and a silicon nitridelayer on the wafer 140, a silicon-containing gas and anoxygen-containing gas and a silicon-containing gas and a nitrogencontaining gas are used, respectively. Also, the source gases may bedivided into two parts according to kinds of the source gasesrespectively, and each part of the source gases may be supplied into thefirst injectors 152 and the second injectors 154, respectively. Whenmolecules of the source gas react well with each other at roomtemperature, the molecules of the source gas are supplied in differentways. For example, in order to form a silicon oxide layer, silane (SiH₄)and oxygen (O₂) are used as the source gas. The silane and the oxygenreact well with each other at room temperature.

[0067] The process gas etches the contaminant particles by an ion impactof plasma reaction. The process gas is selected according to the kind ofthe thin film formed on the wafer 140 and a process condition. Forexample, in order to remove contaminant particles such as silicon orsilicon oxide that deteriorates the characteristics of the thin film, afluorine-containing gas is chosen as the process gas.

[0068] The stabilizing gas stabilizes the process gas. A gas suitablefor removing the contaminant particles from the ion impact of theprocess gas is selected. For example, when trifluoro-nitrogen (NF₃) isused as the process gas, a hydrogen-containing gas is used to removefluorine from trifluoro-nitrogen (NF₃). Not only does the fluorineimprove the characteristics of the thin film, but the fluorine alsoetches the thin film non-uniformly, thereby enhancing uniformity of thethin film. When hydrogen is used, the fluorine in the reaction chamber110 forms hydrogen fluoride that can be removed effectively.

[0069] When the wafer 140 is placed on the electrostatic chuck 120, thegases are supplied into the reaction chamber 110. The gases comprise thesource gas as the first gas for forming the thin film on the wafer 140,the process gas as the second gas for improving the characteristics ofthe thin film and the stabilizing gas as the third gas for stabilizingthe contaminant particles from the process gas to remove.

[0070] When the gases are supplied into the reaction chamber 110, aradio frequency voltage is supplied through a radio frequency coil 182and the electrostatic chuck to form gaseous plasma in the reactionchamber 110. The thin film is formed on the wafer 140 from the plasma ofthe source gas. The contaminant particles may be formed from the plasmaof the source gas. The contaminant particles deteriorate gap-fillingproperties of the thin film, for example, the contaminant particles formvoids in the thin film formed on the wafer 140. The contaminantparticles are reduced when the process gas is supplied into the reactionchamber apart from the wafer. That is, damage by the contaminantparticles is reduced, when a length of the first injector 152 is reducedand the process gas is supplied to the wafer 140 through the reducedfirst injectors 152. However, the first injectors 152 may inject thesource gas for forming the thin film as well as the process gas.

[0071] In the case of an apparatus for depositing the thin film havingpredetermined length of the injectors for depositing the thin filmuniformly on the wafer 140, as a length of the first injectors 152 isshortened, the thin film having a relatively lower thickness isdeposited on the central portion of the wafer 140. The second injectors154 being relatively longer than the first injectors 152 improves theuniformity of the thickness of the thin film. The source gases injectedthrough the second injectors 154 being relatively longer than the firstinjectors 152 are concentrated on the central portion of the wafer 140to deposit relatively more thickly in the central portion of the wafer140 than a peripheral portion of the wafer 140. Therefore, the thin filmis deposited uniformly on the wafer.

[0072] In an exemplary embodiment of the present invention, thegas-supplying unit 150 includes a plurality of injector units. At leastone of the first injectors 152 and at least one of the second injectors154 form at least one injector unit. A plurality of injector units isdisposed on the inside of the reaction chamber 110. An interval betweenat least one of the first injector 152 and the peripheral portion of thewafer 140 is shorter than an interval between the second injectors 154and the central portion of the wafer 140.

[0073]FIG. 8 is a graph illustrating uniformity of the thin film formedon the wafer using the apparatus of FIG. 6.

[0074] Referring to FIG. 8, when the first injectors and the secondinjectors having different lengths than the first injectors are used,the thin film is then deposited more uniformly compared to using thefirst injectors and the second injectors having substantially the samelengths as the first injectors. In FIG. 8, the horizontal axisrepresents the interval between the central portion of the wafer and theperipheral portion of the wafer and the vertical axis represents thethickness of the thin film deposited on the wafer.

[0075] When the thin film is formed using the first injectors and thesecond injectors having different lengths than the first injectors 200,the thickness of the thin film in the central portion of the wafer(point 1) has a larger variance than a thickness of the thin film usingthe first injectors and the second injectors having substantially thesame lengths 210. The thickness of the thin film of the central portionof the wafer (point 1) using the injectors of substantially the samelengths 210 was about 1,750 Å, but the thickness of the thin film of thecentral portion of the wafer using the first injectors and the secondinjectors having different length from the first injectors was about1,980 Å. A difference of the thickness between the thin films decreasesin the peripheral portion of the wafer (point 49). When the injectors210 having the substantially same length were used, the maximumdifference of the thickness between the films deposited on the wafer wasabout 400 Å. However, when the first injectors and the second injectorshaving different length from the first injectors were used, the maximumdifference of the thickness between the films deposited on the wafer wasabout 200 Å.

[0076] According to an exemplary embodiment of the present invention,when the first injectors and the second injectors having differentlength than the first injectors were used, the uniformity of thethickness of the thin film deposited on the wafer increased by about 50%compared with that of the conventional case. That is, the gas issupplied to deposit the thin film uniformly. A flow rate of the gas at acentral portion of a semiconductor substrate is greater than the flowrate at a peripheral portion of the semiconductor substrate.

[0077]FIG. 9 is a graph illustrating uniformity of the thin film formedon the wafer according to another exemplary embodiment of the presentinvention. In FIG. 9, the horizontal axis represents the intervalbetween the central portion of the wafer and the peripheral portion ofthe wafer and the vertical axis represents the thickness of the thinfilm deposited on the wafer.

[0078] Referring to FIGS. 6, 7 and 9, according to another exemplaryembodiment of the present invention, the apparatus for depositing a thinfilm comprises a reaction chamber 110 in which a plasma is generated, awafer holder 130 disposed in the reaction chamber 110 for supporting awafer 140, and gas-supplying unit 150 disposed in the reaction chamber110 for supplying gases into the reaction chamber 110. The gas-supplyingunit 150 supplies a first gas for forming a thin film on the wafer 140,a second gas for improving characteristics of the thin film and a thirdgas for stabilizing the second gas into the reaction chamber 110.

[0079] The gas-supplying unit 150 comprises a first injector 152 and asecond injector 154. The first injector 152 supplies the reactionchamber 110 with a gas such as the first gas, the second gas and thethird gas. The second injector 154 supplies the reaction chamber 110with a gas such as the first gas, the second gas and the third gas.

[0080] A plurality of the first injectors 152 and a plurality of thesecond injectors 154 form at least one injector unit. The firstinjectors 152 are disposed in parallel to the second injectors 154. Thatis, an interval between the first injectors 152 and the wafer 140 isnarrower than an interval between the second injectors 154 and the wafer140.

[0081] The first gas supplied into the reaction chamber 110 includes agas such as a silicon-containing gas, an oxygen-containing gas, anitrogen-containing gas and an inert gas. The second gas may include afluorine-containing gas, and the third gas may include ahydrogen-containing gas so as to stabilize the fluorine-containing gas.For example, when the first gas includes a gas such as a silane gas(SiH₄), oxygen (O₂), nitrous oxygen (N₂O), nitrogen (N₂), helium (He)and argon (Ar), the second gas includes a trifluoro-nitrogen (NF₃) gas,and the third gas includes a hydrogen gas (H₂).

[0082] When the wafer 140 is placed on an electrostatic chuck 120, thefirst gas, the second gas and the third gas are supplied into thereaction chamber 110. The first gas, the second gas and the third gasare supplied into the first injectors 152 and the second injectors 154according to the thin film formed on the wafer 140, respectively. Thatis, the first gas is supplied from under the reaction chamber 110 to topof the reaction chamber 110. The first gas is supplied to beconcentrated on the central portion of the wafer 140. When the gases aresupplied, a radio frequency voltage is supplied to a radio frequencycoil 182 and the electrostatic chuck 120 to form plasma of the gases inthe reaction chamber 110. The thin film is deposited on the wafer 140from the plasma of the first gas and the second gas. Therefore,contaminant particles from the second gas are reacted with the thirdgas, and the contaminant particles are stabilized and removed from thereaction chamber. Although the third gas removes the contaminantparticles, a portion of the contaminant particles may remain in thereaction chamber 110. The contaminant particles may deteriorate agap-filling characteristics of the thin film, for example, thecontaminant particles form voids in the thin film on the wafer 140. Thecontaminant particles may be reduced when the second gas is suppliedinto the reaction chamber apart from the wafer. The second gas causesthe contaminant particles. That is, the control of the length of thefirst injectors 152 and the second injectors 154 may reduce the problemsof deteriorating the gap-filling properties.

[0083] When lengths of the injectors are constant in order to depositthe thin film uniformly on the wafer 140, as the length of the firstinjectors 152 is shortened, the thickness of the thin film deposited onthe central portion of the wafer 140 is relatively thinner than thethickness of the thin film deposited on the peripheral portion of thewafer 140. However, second injectors 154 that is relatively longer thanthe first injectors 152 may improve the uniformity of the thickness ofthe thin film. The source gas injected through the second injectors 154that is relatively longer than the first injectors 152 is concentratedon a central portion of the wafer 140 to deposit relatively thicker thinfilm in the central portion of the wafer 140 than a peripheral portionof the wafer 140. Therefore, the thin film deposits uniformly on thewafer 140. That is, according to another exemplary embodiment of thepresent invention, the problems caused by the contaminant particles arereduced by the control of the lengths of the first injectors 152 and thesecond injectors 154, and damage of the thin film is minimized by meansof the third gas.

[0084] Referring to FIG. 9, forming the thin film using a plurality ofthe first injector, a plurality of the second injector having differentlengths from the first injectors and the third gas 300 shows largerdifference in the thickness of the thin film in the central portion ofthe wafer (point 1) than forming the thin film using a plurality of theinjectors of substantially the same lengths 310. The thickness of thethin film of the central portion of the wafer (point 1) using theinjectors of substantially the same lengths 310 was about 2,900 Å.However, the thickness of the thin film of the central portion of thewafer using the first injectors, the second injectors having differentlengths from the first injectors and the third gas 320 was about 4,400Å. A difference of the thickness between the thin films decreases in theperipheral portion of the wafer (point 49). When the injectors ofsubstantially the same lengths were used, the maximum difference of thethickness between the films deposited on the wafer was about 1,700 Å.However, when the first injectors, the second injectors having differentlengths from the first injectors and the third gas 300 were used, themaximum difference of the thickness between the films deposited on thewafer was about 300 Å. That is, according to another exemplaryembodiment of the present invention, when the thin film was depositedusing the first injectors, the second injectors having different lengthsfrom the first injectors and the third gas, the uniformity of the thinfilm increased by about 85%.

[0085] According to another exemplary embodiment of the presentinvention, the thin film having uniform thickness may be deposited usingthe first injectors, the second injectors having different lengths fromthe first injectors and the third gas. That is, the uniformity of thethin film is increased as well as the thickness of the thin film iscontrolled easily by using a plurality of the injectors having differentlengths with each other.

[0086] In another exemplary embodiment of the present invention, atleast one of the first injectors 152 and at least one of the secondinjectors 154 form at least one injector unit, and a plurality ofinjector units are disposed along the inside of the reaction chamberwith uniform intervals. The gas-supplying unit 150 has a plurality ofthe injectors unit. An interval between the first injectors 152 and theperipheral portion of the wafer 140 is preferably shorter than aninterval between the second injectors 154 and the central portion of thewafer 140. Accordingly, more gas is supplied to the central portion ofthe wafer 140 than the peripheral portion of the wafer 140. Thecontaminant particles formed from the gas for improving thecharacteristics of the thin film are transformed into stable compound todeposit the thin film having uniform thickness on the wafer.

[0087]FIG. 10 is a flow chart illustrating a method of forming a thinfilm according to another exemplary embodiment of the present invention,and FIG. 11 is a graph illustrating characteristics of the thin filmformed on the wafer according to another exemplary embodiment of thepresent invention.

[0088] Referring to FIGS. 10 and 11, a plasma reaction chamber and agas-supplying unit are disposed in an apparatus for depositing a thinfilm (step S11). A semiconductor substrate is then loaded in thereaction chamber (step S12). A first gas for depositing the thin film onthe semiconductor substrate, a second gas for improving a characteristicof the thin film and a third gas for stabilizing the second gas are thensupplied into the reaction chamber sequentially or simultaneously (stepS13). Plasma of the first gas and the second gas is formed in thereaction chamber to form the thin film on the semiconductor substrate(step S14).

[0089] In order to form an oxide layer or a nitride layer on thesemiconductor substrate, the first gas includes a gas such as asilicon-containing gas, an oxygen-containing gas, a nitrogen-containinggas and an inert gas. The second gas includes a fluorine-containing gas.The third gas includes a hydrogen-containing gas that may react with thefluorine-containing gas. For example, when the first gas includes a gassuch as a silane gas (SiH₄), oxygen (O₂), nitrous oxygen (N₂O), nitrogen(N₂), helium (He) and argon (Ar), the second gas includes atrifluoro-nitrogen (NF₃) gas, and the third gas includes a hydrogen gas(H₂). The first gas is selected according to a kind of the thin filmformed on the wafer 140. The second gas has similar characteristics toan etching gas for improving the characteristics of the thin film formedon the semiconductor substrate.

[0090] When the semiconductor substrate is loaded into the reactionchamber, the gases are supplied into the reaction chamber. That is, thefirst gas for forming the thin film, the second gas for improving thecharacteristics of the thin film, and the third gas for stabilizingcontaminant particles formed from the second gas to remove thecontaminant particles are supplied. When the gases are supplied, a radiofrequency voltage is applied to the radio frequency coil and anelectrostatic chuck disposed in the reaction chamber to form plasma ofthe gases in the reaction chamber. The thin film is deposited on thesemiconductor substrate from the plasma of the first gas and the secondgas. The contaminant particles may be formed from the plasma of thesecond gas. The contaminant particles form voids. Therefore, thecontaminant particles hinder a gap-fill by means of the thin film. Thecontaminant particles formed from the second gas are transformed intodifferent compounds using the third gas to reduce the problems of thecontaminant particles. For example, when the first gas includes silane(SiH₄), oxygen (O₂) and helium (He), the second includestrifluoro-nitrogen (NF₃), and the third gas includes hydrogen (H₂), asilicon oxide layer is formed on the semiconductor substrate. A reactionbetween the gases is shown in formula 1.

SiH₄+O₂=SiO₂+2H₂   Formula 1

[0091] Fluorine radicals are formed from the second gas, and thefluorine compounds remain in the reaction chamber to deteriorate thecharacteristics of the thin film. The fluorine compounds are changedinto different compounds as shown by the following exemplary formula 2.

SiH₄+O₂=SiO₂+2H₂   Formula 2

2NF₃+3H₂=N₂+6HF₂

[0092] Generally, as the semiconductor device becomes highly integrated,intervals between patterns formed on the semiconductor substrate areshortened, and the height of the patterns is increased. The intervalsbetween the patterns are the intervals between individual elements ormetal patterns, or a width of shallow trench isolation (STI). As theaspect ratio (length/width) of the pattern of the thin film increases,deposition of the thin film becomes more difficult. In an HDP-CVD, thedeposition of the thin film and the etching of the thin film areperformed simultaneously. When the width of the patterns of thesemiconductor substrate is narrow, the thin film formed on the patternsis etched by means of the plasma. Therefore, the thin film isredeposited to form voids in the thin film deposited on the patterns.When hydrogen is added to the gases, both the etching of the thin filmby the plasma and the redeposition rate decrease. As the redepositionrate decreases, bias power may increase and the characteristics of thethin film may be improved.

[0093] In FIG. 11, the horizontal axis represents the interval betweenthe central portion of the wafer and the peripheral portion of thewafer, and the vertical axis represents the deposition rate according toa sputter rate (S/D). Here, the sputter rate is the etching rate.

[0094] Referring to FIG. 11, when the S/D increases, the thin film maybe over-etched to cause redeposition. The S/D of the central portion ofthe semiconductor substrate (point 1) was about 0.13 without the thirdgas (denoted by reference numeral 400). However, when a flow rate of thethird gas was between about 150 sccm and about 500 sccm, the S/D of thecentral portion of the semiconductor substrate (point 1) decreases. Thedecrease of the S/D means a proportional decrease of the thin filmetched, when the substantially same amount of the thin film isdeposited.

[0095] When the flow rate of the third gas was about 150 sccm (denotedby reference numeral 410), the S/D of the central portion of thesemiconductor substrate (point 1) was about 0.07. Therefore, when theflow rate of the third gas was about 150 sccm, the S/D differencebetween the central portion of the semiconductor substrate (point 1) andthe peripheral portion of the semiconductor substrate (point 49) weresubstantially the same. However, the S/D of the central portion of thesemiconductor substrate (point 1) was about a half compared with thecase without the third gas.

[0096] Also, when the flow rate of the third gas was about 300 sccm(denoted by reference numeral 420), the S/D of the central portion ofthe semiconductor substrate (point 1) was about 0.05. Therefore, whenthe flow rate of the third gas was about 300 sccm, the S/D differencebetween the central portion of the semiconductor substrate (point 1) andthe peripheral portion of the semiconductor substrate (point 49) wasabout 0.02. However, the S/D of the central portion of the semiconductorsubstrate (point 1) was about two thirds compared with the case withoutthe third gas.

[0097] When the flow rate of the third gas was about 500 sccm (denotedby reference numeral 430), the S/D of the central portion of thesemiconductor substrate (point 1) was about 0.03. Therefore, the S/Ddifference between the central portion of the semiconductor substrate(point 1) and the peripheral portion of the semiconductor substrate(point 49) was about 0.05. However, the S/D of the central portion ofthe semiconductor substrate (point 1) was about five sixths comparedwith the case without the third gas.

[0098] When the S/D without the redeposition was 0.13, the S/D of about500 sccm was one fourth of the S/D without the redeposition. Therefore,the bias power may be increased by about four times. When bias powerincreases, the characteristics of the thin film formed on thesemiconductor substrate may be improved. However, as the flow rate ofthe third gas increases, the S/D between the central portion of thesemiconductor (point 1) and the peripheral portion of the semiconductor(point 29) also increases. Therefore, the semiconductor substrate ispartially over-etched. Referring to FIG. 11, a step of the S/D graph isshown in the middle portion (point 25) disposed between the centralportion of the semiconductor substrate and the peripheral portion of thesemiconductor substrate. However, the control of the lengths of thefirst and the second injectors of the gas-supplying unit may reduce thestep.

[0099] According to the present invention, when the first injectors andthe second injectors having different lengths from the first injectorsare used, or when the first injectors, the second injectors havingdifferent length from the first injectors and a stabilizing gas areused, uniformity of thin film deposited on a wafer is increased. Thatis, a flow rate of the first gas at a central portion of thesemiconductor substrate is greater than at a peripheral portion of thesemiconductor substrate, and contaminant particles formed from a gas aretransformed to stable compound so as to improve thin filmcharacteristics, thereby depositing the thin film uniformly on thewafer.

[0100] While the present invention has been particularly shown anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present invention as defined by the following claims.

What is claimed is:
 1. A method of forming a thin film comprising:supplying a first gas for forming a thin film onto a semiconductorsubstrate, a second gas for improving characteristics of the thin filmand a third gas for stabilizing the second gas; and forming the thinfilm on the semiconductor substrate using plasmas of the first andsecond gases.
 2. The method of forming a thin film of claim 1, whereinthe first gas includes at least one gas selected from the groupconsisting of a silicon-containing gas, an oxygen-containing gas, anitrogen-containing gas and an inert gas.
 3. The method of forming athin film of claim 2, wherein the second gas includes afluorine-containing gas and the third gas includes a hydrogen-containinggas.
 4. The method of forming a thin film of claim 1, wherein the firstgas includes at least one gas selected from the group consisting of asilane gas, an oxygen gas, a nitrous oxygen gas, a nitrogen gas, ahelium gas and an argon gas, the second gas includes atrifluoro-nitrogen gas, and the third gas includes a hydrogen gas. 5.The method of forming a thin film of claim 4, wherein the forming of thethin film includes forming at least one of an oxide layer and a nitridelayer on the semiconductor substrate.
 6. The method of forming a thinfilm of claim 1, wherein a flow rate of the first gas at a centralportion of the semiconductor substrate is greater than the flow rate ofthe first gas at a peripheral portion of the semiconductor substrate. 7.An apparatus for forming a thin film comprising: a reaction chamber; awafer holder for supporting a wafer, the wafer holder being disposed inthe reaction chamber; and a gas-supplying unit extended into thereaction chamber to supply a gas, wherein the flow rate of the suppliedgas at the central portion of the wafer is greater than the flow rate ofthe supplied gas at a peripheral portion of the wafer.
 8. The apparatusfor forming a thin film of claim 7, wherein the gas-supplying unitincludes at least one injector, and the injector extends into aninterior of the reaction chamber.
 9. The apparatus for forming a thinfilm of claim 8, wherein the gas-supplying unit includes a plurality offirst injectors adjacent to peripheral portions of the wafer andextending into the interior of the reaction chamber, and a plurality ofsecond injectors adjacent to a central portion of the wafer andextending into the interior of the reaction chamber.
 10. The apparatusfor forming a thin film of claim 8, wherein at least one of the firstinjectors and at least one of the second injectors form at least oneinjector unit, and a plurality of injector units are disposed on theinterior of the reaction chamber.
 11. The apparatus for forming a thinfilm of claim 9, wherein an interval between the first injector and theperipheral portions of the wafer is shorter than an interval between thesecond injector and the central portion of the wafer.
 12. An apparatusfor forming a thin film comprising: a reaction chamber; a wafer holderfor supporting a wafer, the wafer holder being disposed in the reactionchamber; and a gas-supplying unit disposed in the reaction chamber tosupply a first, a second and a third gas into the reaction chamber,wherein the first gas forms a thin film on the wafer, the second gasimproves characteristics of the thin film, and the third gas stabilizesthe second gas.
 13. The apparatus for forming a thin film of claim 12,wherein the first gas includes at least one gas selected from the groupconsisting of a silicon-containing gas, an oxygen-containing gas, anitrogen-containing gas and an inert gas.
 14. The apparatus for forminga thin film of claim 13, wherein the second gas includes afluorine-containing gas and the third gas includes a hydrogen-containinggas.
 15. The apparatus for forming a thin film of claim 14, wherein: thefirst gas includes at least one gas selected from the group consistingof a silane gas, an oxygen gas, a nitrous oxygen gas, a nitrogen gas, ahelium gas and an argon gas; the second gas includes atrifluoro-nitrogen gas; and the third gas includes a hydrogen gas. 16.The apparatus for forming a thin film of claim 12, wherein thegas-supplying unit includes a plurality of first injectors for supplyingat least one gas selected from the group consisting of the first gas,the second gas and the third gas, and a plurality of second injectorsfor supplying at least one gas selected from the group consisting of thefirst gas, the second gas and the third gas.
 17. The apparatus forforming a thin film of claim 16, wherein an injector unit comprises atleast one of the first injectors and at least one of the secondinjectors, and a plurality of injector units is installed along an innerface of the reaction chamber.
 18. The apparatus for forming a thin filmof claim 17, wherein an interval between the first injectors and theperipheral portion of the wafer is shorter than an interval between thesecond injectors and the central portion of the wafer.